PaymentHandler: Implement PaymentRequestEvent constructor.

third_party/WebKit/Source/modules/payments/PaymentRequestEventInit.idl

Index: third_party/WebKit/Source/modules/payments/PaymentRequestEventInit.idl
diff --git a/third_party/WebKit/Source/modules/payments/PaymentRequestEventInit.idl b/third_party/WebKit/Source/modules/payments/PaymentRequestEventInit.idl
index 8ad64f1e1a3e2a8f90c1d13dd13c5936d34464eb..66f3287b87cb2638f6001c474a66ac707219a79a 100644
--- a/third_party/WebKit/Source/modules/payments/PaymentRequestEventInit.idl
+++ b/third_party/WebKit/Source/modules/payments/PaymentRequestEventInit.idl
@@ -4,11 +4,9 @@
 
 // https://w3c.github.io/payment-handler/#paymentrequesteventinit-dictionary
 
-// TODO(zino): Once the spec issue is resolved, we should apply the changes.
-// Please see https://github.com/w3c/payment-handler/pull/162
-dictionary PaymentRequestEventInit {
-    DOMString topLevelOrigin;
-    DOMString paymentRequestOrigin;
+dictionary PaymentRequestEventInit : ExtendableEventInit {
+    USVString topLevelOrigin;
+    USVString paymentRequestOrigin;
     DOMString paymentRequestId;
     sequence<PaymentMethodData> methodData;
     PaymentItem total;